The present application relates to a thin film transistor, a method for manufacturing a thin film transistor, and an electronic apparatus. In particular, the present application relates to a bottom contact type thin film transistor, in which a semiconductor thin film is disposed as a layer on a source electrode and a drain electrode, a method for manufacturing the thin film transistor, and furthermore, an electronic apparatus including the thin film transistor.
In recent years, a thin film transistor (TFT) including an organic semiconductor thin film serving as an active layer, that is, a so-called organic thin film transistor (hereafter abbreviated as organic TFT) has been noted. The organic TFT is advantageous for cost reduction because the organic semiconductor thin film serving as an active film can be formed through coating film formation at low temperatures. Furthermore, formation on a flexible substrate, e.g., plastic, having low heat resistance is possible. Therefore, the organic TFT has been noted as a drive element of a thin film display device as well.
Regarding such an organic TFT, it has been understood that the film quality of the organic semiconductor thin film serving as an active layer depends on properties of a base material surface significantly. Consequently, in production of the organic TFT, in order to improve the device characteristics, it has been attempted to form an organic semiconductor thin film having good quality by devising the material for a base material itself or reforming the base material surface before formation of the organic semiconductor thin film.
For example, a material suitable for a substrate or a gate insulating film, which serve as a base material of the organic semiconductor thin film, is selected from wide variety of materials from inorganic compounds to organic polymer compounds and is used, so that growth of the organic semiconductor thin film on the substrate or the gate insulating film is facilitated. On the other hand, the materials selected for the source electrode and the drain electrode are limited from the viewpoint of the electrical conductivity and the like. Consequently, growth of the organic semiconductor thin film on the source electrode and the drain electrode is facilitated by subjecting these electrodes to a surface treatment with, for example, a thiol molecule.
Besides, “IEEE ELECTRON DEVICE LETTERS”, VOL. 18, NO. 12, p. 606-608, 1997 discloses that a source electrode and a drain electrode are formed from gold (Au) on a gate insulating film formed from silicon oxide (SiO2) and, thereafter, a treatment by using an ethanol solution of octadecyltrichlorosilane (OTS) is conducted, so as to form a unimolecular film on SiO2 through self organization and reform the surface of the gate insulating film serving as a base material of an organic semiconductor thin film.
Furthermore, for example, Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-503026 discloses a method in which in disposition of a self-organized unimolecular layer to reform a base material of the organic semiconductor thin film on a surface of a gate insulating film serving as a base material for an organic semiconductor thin film, this self-organized unimolecular layer is formed as a reaction product of the gate insulating film and a precursor of the self-organized unimolecular layer.